1. Technical Field
The technology disclosed herein relates to a lens barrel for supporting an optical system.
2. Background Information
Digital cameras that make use of image sensors such as a Charge Coupled Device (CCD) or Complementary Metal-oxide Semiconductor (CMOS) sensor to convert an optical image into an electrical signal, and record by digitizing the electrical signal, have grown to be popular in recent years.
In the field of digital cameras, the overall size of the camera needs to be reduced in order to make the product more portable. More specifically, a more compact lens barrel has been proposed in order to make the camera body thinner.
With the lens barrel discussed in Japanese Patent Laid-Open Publication No. JP2003-066308, a rotating tube 25 is arranged to guide in the optical axis direction a forward movement tube 26 that supports a first lens group 11, and a first moving tube 20 that supports a second lens group 12. Cam grooves that guide the forward movement tube 26 and the first moving tube 20 are arranged on the outer peripheral part and inner peripheral part of the rotating tube 25.
However, if the forward movement tube 26 and the first moving tube 20 rotate along with the rotating tube 25, the forward movement tube 26 and the first moving tube 20 will not be guided by the cam grooves.
In view of this, an outer rectilinear tube 24 and an inner rectilinear tube 23 are arranged on the outer peripheral side and inner peripheral side of the rotating tube 25 in order to restrict the rotation of the forward movement tube 26 and the first moving tube 20. The outer rectilinear tube 24 and the inner rectilinear tube 23 are coupled to the rotating tube 25 with bayonet coupling so that the outer rectilinear tube 24 and the inner rectilinear tube 23 will move integrally in the optical axis direction with the rotating tube 25. Rotation of the forward movement tube 26 and the first moving tube 20 is restricted by the outer rectilinear tube 24 and the inner rectilinear tube 23, and the forward movement tube 26 and the first moving tube 20 are guided in the optical axis direction by the cam grooves.
If two rectilinear tubes are arranged on the outer peripheral side and inner peripheral side of the rotating tube 25, however, this means more parts are required, which hampers efforts to make the lens barrel more compact. Furthermore, since bayonets must be arranged on the rotating tube 25, the outer rectilinear tube 24, and the inner rectilinear tube 23, the size of the tubes in the optical axis direction becomes larger, which also is contrary to the goal of making the lens barrel smaller in the optical axis direction.
Also, a structure in which the various lens frames are guided by a shaft has been conceived, as disclosed in Japanese Patent Laid-Open Publication No. JP2007-211792.
Providing a shaft, though, makes it more difficult to dispose the lens frames efficiently, and so is contrary to the goal of making the lens barrel smaller in the optical axis direction.